1. Field of the Invention
The present invention relates to a web dryer such as for use in drying of a web in the printing industry, and more particularly, pertains to a highly compact air flotation dryer which uses internal solvent-laden air as a combustion medium to generate high internal drying temperatures for use in drying a web and thereby minimizing solvent-laden air exhausted into the atmosphere.
2. Description of the Prior Art
Prior art web dryers were notorious in being operationally inefficient in web drying, consuming large amounts of physical floor space, and lacking in sophisticated computerized monitoring and control of the web dryer. Prior art web dryers attempted to reduce to a negligible amount the solvent concentration exhausted into the atmosphere through a variety of methods such as by using incinerators to combust the solvents in the dryer air, then attempting to recover the heat from the burned or combusted solvents by heat exchangers. Other methods include removing solvents from the air with the use of catalytic converters.
Two representative prior art patents are "Method and Apparatus for Purifying Exhaust Air of a Dryer Apparatus", U.S. Pat. No. 3,875,678 and "Method of Curing Strip Coating", U.S. Pat. No. 4,206,553. Both of these patents disclose prior art dryers as discussed above.
The present invention overcomes the disadvantages of the prior art by providing coordinated control of built-in exhaust fan speed, damper vanes, burner pressures and box pressures to maintain optimum combustion chamber temperature, supply air temperature, supply air flow, solvent concentration (LFL) and exhaust air rate.